As a communicating system wherein communicating terminals, such as mobile telephones, are used, the PoC (Push-to-talk over Cellular) system has been commercially made available. The PoC system is advantageous in that a user with a communicating terminal performs audio transmission to other users at the same time, namely one-to-many communication is performed, and is attracting attention as a handy communication tool used by a plurality of different groups of users. In the PoC system, however, it is not possible for two or more users to perform the audio transmission at the same time, and the user must push a button for speech provided in the communicating terminal and obtains a speech right before he/she starts to talk. The audio of the speech, which is obtained until the pushed button for speech is released so that the speech right is resigned, is transmitted to the other communicating terminals simultaneously, and the other users simultaneously listen to them. The other users can not obtain the speech right while the one user is speaking, which makes it necessary for the plurality of users to transfer to one another for the speech right during the communication in the PoC system.
The PoC system is provided with a server for the administration of the speech right and the transmission and reception of the audio data. The server approves the speech by giving the speech right to any of the communicating terminals when the speech right is thereby requested, and receives the audio data transmitted from the communicating terminal allowed to speak, and transmits the received audio data to the other communicating terminals simultanously. The server is adapted to simultaneously transmit the audio data to the communicating terminals included in a communication group registered in advance, and is responsible for processes associated with the administration of the communication group.
According to the Japanese Laid-open Patent Publication No. 2006-180143, a communicating system is discussed. With the communicating system, a mobile terminal makes an appointment for the speaker's right in a PoC server, and the speaker's right is given on a first-come first-served basis after it is released, so that the user conveniently speak. In the communicating system, the PoC server sets an appointment status of the speaker's right in an administering table, and the appointment is registered or cancelled by a notice sent by pushing a PoC key provided on the mobile terminal. The mobile terminal displays the appointments for the speaker's right in the PoC server and notifies information indicating that another appointment is made using a vibrator when the speaker's right is retained. The PoC server allocates the speaker's right to the mobile terminals in order of the appointment registrations, and releases the speaker's right in a case where there is no response from the user when the speaker's right is allocated.